1. Field of the Invention
The present invention relates to isolated polypeptides having feruloyl esterase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.
2. Description of the Related Art
Polysaccharides constitute 90% of plant cell walls and can be divided into three groups: cellulose, hemicellulose, and pectin. Cellulose represents the major constituent of cell wall polysaccharides. Hemicelluloses are the second most abundant constituent of plant cell walls. The major hemicellulose polymer is xylan. The structure of xylans found in cell walls of plants can differ significantly depending on their origin, but they all contain a beta-1,4-linked D-xylose backbone. The beta-1,4-linked D-xylose backbone can be substituted by various side groups, such as L-aribinose, D-galactose, acetyl, feruloyl, p-coumaroyl, and glucuronic acid residues.
The biodegradation of the xylan backbone depends on two classes of enzymes: endoxylanases and beta-xylosidases. Endoxylanases (EC 3.2.1.8) cleave the xylan backbone into smaller oligosaccharides, which can be further degraded to xylose by beta-xylosidases (EC 3.2.1.37). Other enzymes involved in the degradation of xylan include, for example, acetylxylan esterase, arabinase, alpha-glucuronidase, feruloyl esterase, and p-coumaric acid esterase.
Faulds and Williamson, 1991, J. Gen. Microbiol. 137: 2339-2345, describe the purification and characterization of 4-hydroxy-3-methoxy-cinnamic (ferulic) acid esterase from Streptomyces olivochromogenes. Faulds and Williamson, 1994, Microbiology 140: 779-787, describe the purification and characterization of a feruloyl esterase from Aspergillus niger. Kroon et al., 1996, Biotechnol. Appl. Biochem. 23: 255-262, describe the purification and characterisation of a novel feruloyl esterase induced by growth of Aspergillus niger on sugarbeet pulp. deVries et al., 1997, Appl. Environ. Microbiol. 63: 4638-4644, disclose feruloyl esterase genes from Aspergillus niger and Aspergillus tubingensis. Castanares et al., 1992, Enzyme Microbiol. Technol. 14: 875-884, describe the purification and properties of a feruloyl/p-coumaroyl esterase from the fungus Penicillium pinophilum. 
The present invention relates to polypeptides having feruloyl esterase activity and polynucleotides encoding the polypeptides.